1. Field of the Invention
The present invention relates generally to mixing solutions and more specifically to a wrap spring clutch syringe ram which mixes precise amounts of solutions.
2. Discussion of Prior Art
There are two existing clutched rapid-reaction syringe rams. However, neither is commercially available. The first device is described by H. Gutfreund (Methods in Enzymology XVI, 1969, pp 229–249, ed. Kenneth Kustin, Academic Press, New York). Gutfreund used a 700 rpm motor coupled to a firmly engaging magnetic clutch and a magnetic brake. The microswitches which controlled the clutch and the brake were operated by a lever which moved with the syringe barrier.
A second device was reported in the doctoral thesis of David P. Ballou, 1971, Biochemistry, University of Michigan. His device employed a silicone-controlled-rectifier (SRC) controlled DC motor which turned a Volkswagen flywheel. The flywheel engaged a gearbox, which drove a flat, spiral-shaped, snail-shell-like cam, the slope of which pushed a cam follower, which pushed the syringes until the maximum diameter of the cam was reached. The output of the gearbox was a rotating table, and the cam was a separate disk which laid flat and motionless on top of the rotating table, mounted on a central shaft and bearing. Although it is not clear from his thesis, it appears that the cam could be engaged positively to the rotating table to initiate a push, by a pin that operated as a clutch. Apparently the clutch pin was pressed manually through a hole in the cam, so that the clutch pin extended through the cam and into a matching hole drilled into the rotating table.
A single-stop, or a multiple-stop, wrap spring clutch could be incorporated between the gearbox and the cam, or between the flywheel and the gearbox, of Professor Ballou's design, to enable multiple pushes. This cam design of wrap spring clutch syringe ram is discussed below, with reference to FIGS. 15 and 16.
A non-clutched rapid-reaction syringe ram manufactured by Update Instruments (United States) is referred to in the Summary of Invention section. The Update Instruments design utilizes a low inertial DC motor coupled to an optical encoder. Manufacturers of non-clutched rapid-reaction syringe rams that utilize stepper motors include Bio-Logic (France), Hi-Tech (England), and KinTek (United States).
The original rapid-reaction device of Hartridge and Roughton of 1923, placed each reactant into a separate pressurized vessel, and drained the two solutions simultaneously from their respective vessels down separate lines that joined together at a “Y”. The reaction commenced at the “Y” junction, where the two solutions met and mixed, and the period of reaction was determined by the rate of flow of the mixed solution down the exit tube of the “Y”, and by the volume of the exit tube, or delay line. The detector was placed at various points along the delay line, to monitor the extent of reaction verses period of flow after mixing.
An early version of a rapid-reaction ram was constructed by R. C. Bray in 1961. The syringe ram was driven by a piston, which was driven by hydraulic fluid. Pressurized gas was applied over the hydraulic fluid, which was contained in a reservoir. The hydraulic fluid was dispensed to the piston which drove the syringe ram, by means of an adjustable valve to determine rate of flow, and by an electrically-triggered, on-off valve, which immediately started and stopped the flow of hydraulic fluid, and thus the advancement of the ram. With the on-off valve open, the speed of the syringe ram was determined by the pressure over the fluid, by the degree of opening or closure of the adjustable valve, by the surface area of the top of the piston, by the friction of the ram, and by the back pressure of the syringes.
Several companies, such as OLIS Incorporated, manufacture stopped-flow devices, that are used to push syringes and to mix solutions rapidly for study of chemical and biochemical reactions. Stopped-flow devices usually employ a pressurized-gas-driven piston to push the syringes. Solutions are ejected rapidly from the syringes, through a mixing chamber, thence into an observation cell, and rapidly into an opposing syringe. When the opposing syringe is filled to a predetermined volume, flow immediately stops, and the syringe plunger of the filled stopping syringe trips a switch which initiates data collection. These pressurized-gas-driven, stopped-flow syringe rams may be considered to be simplified versions of the more precise, motor-driven, rapid-reaction syringe rams already mentioned.
Harvard Instruments, of Massachusetts, manufactures syringe pumps that usually are used for slow infusion. These pumps may employ synchronous electric motors and gear boxes, or programmable stepper motors, to push syringes at a defined rate. Other companies manufacture similar units.
Warner Electric manufactures programmable linear actuators that couple any one of several types of electric motors to a screw drive for precise linear motion and positioning. These actuators are comparable to the present invention, however they do not employ a flywheel, or a wrap spring clutch. Their systems appear to be designed for use in automated manufacturing, rather than for the purpose of pushing syringes per our application. The wrap spring clutch used in our system was manufactured by Warner Electric. There are many manufacturers of linear actuators, and of wrap spring clutches.
It also is possible that the present invention may have applications other than just pushing syringes.